JP2013030627A - Photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount a bypass diode on a photoelectric conversion device without degrading a power generation coefficient per installation area.SOLUTION: In a region where a photoelectric conversion unit 102 is formed, a photoelectric conversion cell is connected to a bypass diode 114 through a tab electrode 107 formed from conductive tape.

Description

  The present invention relates to a photoelectric conversion device.

  As a power generation system using sunlight, a photoelectric conversion device in which semiconductor thin films such as amorphous and microcrystals are stacked is used.

  In the photoelectric conversion device, a plurality of photoelectric conversion cells are connected in series and parallel so that a practical electrical output can be taken out. Specifically, a photoelectric conversion module is formed by connecting a plurality of photoelectric conversion cells and enclosing with a filler mainly composed of a translucent substrate and an ethylene vinyl acetate copolymer (EVA). When such a photoelectric conversion module is installed outdoors, when power generation becomes insufficient, such as when a certain photoelectric conversion cell in the photoelectric conversion module becomes a shadow, the photoelectric conversion cell It becomes. At this time, a potential difference of the product of the resistance value and the flowing current is generated in both electrodes of the photoelectric conversion cell. That is, a reverse bias voltage is applied to the photoelectric conversion cell, and the cell generates heat. Such a situation is called a hot spot. If the phenomenon of this hot spot occurs and the temperature of the photoelectric conversion cell continues to rise, in the worst case, the photoelectric conversion cell is destroyed, and a predetermined electric output cannot be taken out from the photoelectric conversion module.

  Therefore, in order to prevent damage to the photoelectric conversion module due to hot spots, a method of connecting a bypass diode to the photoelectric conversion cell so as to be reverse-biased with respect to the normal output is employed. By providing a bypass diode, even if a photoelectric conversion cell somewhere is in the shade and the amount of power generation falls, the current flows through the bypass diode avoiding that portion, so the influence of the shaded part is affected by the circuit It will not extend to the whole.

For example, a plurality of thin film photoelectric conversion cells formed on the main surface of the substrate and connected in series, and a plurality of thin film photoelectric conversion cells connected in series and a plurality of bypass diodes connected in parallel, respectively. And the number n, the reverse withstand voltage V _a of each thin film photoelectric conversion cell, and the open circuit voltage V _{b of} each thin film photoelectric conversion cell satisfy a relationship of inequality n ≦ V _a / V _b +1. A technology to be configured is disclosed (see Patent Document 1).

  Also disclosed is a configuration in which a chip diode is applied as a bypass diode and the chip diode is connected to a copper foil as a lead terminal by solder paste. Here, it is said that it is preferable to mix conductive particles having higher conductivity than solder in the solder paste (see Patent Document 2).

JP 2001-68696 A Japanese Patent Laid-Open No. 9-82865

  By the way, in the said conventional photoelectric conversion apparatus, many photoelectric conversion cells are connected in series and parallel, and the process which arrange | positions a bypass diode discretely with respect to a photoelectric conversion cell, and is electrically connected is required.

  Here, when the bypass diode is arranged outside the photoelectric conversion device, the installation area as the photoelectric conversion module is increased, which causes a decrease in power generation efficiency per installation area. Therefore, it is desired to realize a configuration in which the bypass diode is arranged in the photoelectric conversion region without deteriorating the characteristics of the photoelectric conversion device.

  One aspect of the present invention is a photoelectric conversion device in which a photoelectric conversion unit in which a plurality of photoelectric conversion cells including a thin film semiconductor layer are connected in series is formed on a substrate, and in the region where the photoelectric conversion unit is formed. A photoelectric conversion device in which a photoelectric conversion cell is connected to a plurality of bypass diodes via electrodes made of conductive tape.

  According to the present invention, the bypass diode can be provided in the photoelectric conversion device without reducing the power generation efficiency per installation area.

It is a top view which shows the structure of the photoelectric conversion apparatus in embodiment of this invention. It is sectional drawing which shows the structure of the photoelectric conversion apparatus in embodiment of this invention. It is sectional drawing which shows the structure of the photoelectric conversion apparatus in embodiment of this invention. It is sectional drawing which shows the structure of the photoelectric conversion apparatus in embodiment of this invention. It is an expanded sectional view which shows the structure of the photoelectric conversion unit in embodiment of this invention.

  As shown in the plan view of FIG. 1 and the cross-sectional views of FIGS. 2 to 4, the photoelectric conversion device 100 in the embodiment of the present invention includes a substrate 10, a photoelectric conversion unit 102, an insulating member 104, tab electrodes 106, 107, The lead electrode 108, the insulating member 110, the bypass electrode 112, the bypass diode 114, the back sheet 116, the filler 118, and the terminal box 120 are configured. FIG. 1 is a view showing the structure through the back sheet 116 and the filler 118 in order to clearly show the configuration of the photoelectric conversion device 100. 2 is a cross-sectional view taken along line aa in FIG. 1, FIG. 3 is a cross-sectional view taken along line bb in FIG. 1, and FIG. 4 is taken along line cc in FIG. FIG.

  The photoelectric conversion unit 102 is formed on the substrate 10 as shown in the enlarged sectional view of FIG. With the substrate 10 as the light incident side, from the light incident side, the transparent electrode layer 12, the amorphous silicon photoelectric conversion unit (a-Si unit) 14 having a wide band gap as the top cell, the intermediate layer 16, and the a-Si unit 14 as the bottom cell. It has a structure in which a microcrystalline silicon photoelectric conversion unit (μc-Si unit) 18 and a back electrode layer 20 having a narrower band gap are stacked. In this embodiment, a tandem photoelectric conversion device in which the a-Si unit 14 and the μc-Si unit 18 are stacked will be described as an example. However, the scope of the present invention is not limited to this, A single-type photoelectric conversion device using only one of the a-Si unit 14 and the μc-Si unit 18 or a photoelectric conversion device to which another type of photoelectric conversion unit is applied may be used.

For the substrate 10, for example, a material having transparency in at least the visible light wavelength region, such as a glass substrate or a plastic substrate, can be applied. A transparent electrode layer 12 is formed on the substrate 10. The transparent electrode layer 12 is doped with tin oxide (SnO ₂ ), zinc oxide (ZnO), indium tin oxide (ITO), etc. with tin (Sn), antimony (Sb), fluorine (F), aluminum (Al), etc. It is preferable to use at least one or a combination of a plurality of transparent conductive oxides (TCO). In particular, zinc oxide (ZnO) is preferable because it has high translucency, low resistivity, and excellent plasma resistance. The transparent electrode layer 12 can be formed by, for example, a sputtering method or a CVD method.

When the photoelectric conversion device 100 has a configuration in which a plurality of cells are connected in series, a slit S1 in which the surface of the substrate 10 is exposed is formed in the transparent conductive layer 12 as shown in FIGS. Patterning is performed so that the conductive layer 12 has a strip shape. Further, as shown in the plan view of FIG. 1, a slit S2 in which the surface of the substrate 10 is exposed is formed in a direction intersecting the extending direction of the slit S1, and a plurality of series-connected photoelectric conversion cell groups are arranged in parallel. It is good also as a structure. For example, the transparent electrode layer 12 can be patterned into a strip shape using a YAG laser having a wavelength of 1064 nm, an energy density of 13 J / cm ² , and a pulse frequency of 3 kHz.

An a-Si unit 14 is formed by sequentially laminating a p-type layer, an i-type layer, and an n-type silicon thin film on the transparent electrode layer 12. The a-Si unit 14 includes a silicon-containing gas such as silane (SiH ₄ ), disilane (Si ₂ H ₆ ), dichlorosilane (SiH ₂ Cl ₂ ), a carbon-containing gas such as methane (CH ₄ ), diborane (B ₂ H). ₆ ) Plasma chemical vapor deposition in which a mixed gas obtained by mixing a p-type dopant-containing gas, such as phosphine (PH ₃ ), and a mixed gas, such as phosphine (PH ₃ ), and a diluent gas, such as hydrogen (H ₂ ), is converted into plasma. It can be formed by the method (CVD method). As the plasma CVD method, for example, an RF plasma CVD method of 13.56 MHz is preferably applied.

  An intermediate layer 16 is formed on the a-Si unit 14. The intermediate layer 16 is preferably made of a transparent conductive oxide (TCO) such as zinc oxide (ZnO) or silicon oxide (SiOx). In particular, it is preferable to use zinc oxide (ZnO) or silicon oxide (SiOx) doped with magnesium (Mg). The intermediate layer 16 can be formed by, for example, sputtering. The thickness of the intermediate layer 16 is preferably in the range of 10 nm to 200 nm. The intermediate layer 16 need not be provided.

On the intermediate layer 16, a μc-Si unit 18 in which a p-type layer, an i-type layer, and an n-type layer are stacked in this order is formed. The μc-Si unit 18 includes silicon-containing gas such as silane (SiH ₄ ), disilane (Si ₂ H ₆ ), dichlorosilane (SiH ₂ Cl ₂ ), carbon-containing gas such as methane (CH ₄ ), diborane (B ₂ H ₆ ) formed by a plasma CVD method in which a mixed gas obtained by mixing a p-type dopant-containing gas such as phosphine (PH ₃ ) and a dilute gas such as phosphine (PH ₃ ) and hydrogen (H ₂ ) is formed into a plasma. can do. As with the a-Si unit 14, for example, a 13.56 MHz RF plasma CVD method is preferably applied to the plasma CVD method.

When a plurality of photoelectric conversion cells are connected in series, the a-Si unit 14, the intermediate layer 16, and the μc-Si unit 18 are patterned into strips as shown in FIGS. 1, 2, and 4. A slit S3 is formed by irradiating the YAG laser in parallel along the slit S1 at a position about 50 μm from the patterning position of the slit S1 for dividing the transparent conductive layer 12, and the a-Si unit 14, the intermediate layer 16 and μc are formed. -The Si unit 18 is patterned into a strip shape. For example, a YAG laser having an energy density of 0.7 J / cm ³ and a pulse frequency of 3 kHz is preferably used.

A back electrode layer 20 is formed on the μc-Si unit 18. The back electrode layer 20 preferably has a structure in which a transparent conductive oxide (TCO) and a reflective metal are sequentially laminated. As the transparent conductive oxide (TCO), a transparent conductive oxide (TCO) such as tin oxide (SnO ₂ ), zinc oxide (ZnO), indium tin oxide (ITO), or these transparent conductive oxides A material (TCO) doped with impurities is used. For example, zinc oxide (ZnO) doped with aluminum (Al) as an impurity may be used. Moreover, as a reflective metal, metals, such as silver (Ag) and aluminum (Al), can be used. The transparent conductive oxide (TCO) can be formed by, for example, a sputtering method or a CVD method. The back electrode layer 20 is preferably about 1 μm in total. It is preferable that at least one of the back electrode layers 20 is provided with unevenness for enhancing the light confinement effect.

When a plurality of cells are connected in series, the a-Si unit 14, the intermediate layer 16, the μc-Si unit 18, and the back electrode layer 20 are patterned into strips as shown in FIGS. 1, 2, and 4. A slit S4 is formed by irradiating a YAG laser parallel to the slits S1 and S3 at a position about 50 μm from the patterning position of the slit S3 to form the a-Si unit 14, the intermediate layer 16, the μc-Si unit 18, and The back electrode layer 20 is patterned into a strip shape. A YAG laser having an energy density of 0.7 J / cm ³ and a pulse frequency of 4 kHz is preferably used.

  Thereby, the back electrode layer 20 of one photoelectric conversion cell is electrically connected to the transparent electrode layer 12 of the adjacent photoelectric conversion cell via the back electrode layer 20 embedded in the slit S3, and the adjacent photoelectric conversion cells are connected to each other. Are connected in series.

  Further, as shown in FIG. 1, the slit S5 is formed by irradiating the YAG laser so as to overlap the slit S2, and the a-Si unit 14, the intermediate layer 16, the μc-Si unit 18 and the back electrode layer 20 are removed. The photoelectric conversion cells are separated in parallel. The width of the slit S5 is preferably narrower than the width of the slit S2. The slit S5 can be formed under the same conditions as the slit S4.

  Further, as shown in FIG. 2, the transparent conductive layer 12, the a-Si unit 14, the intermediate layer 16, the μc-Si unit 18, and the back electrode so that the surface of the substrate 10 is exposed in the peripheral portion d of the photoelectric conversion device 100. Layer 20 may be removed. Thereby, when attaching a support frame etc. to the photoelectric conversion apparatus 100, electrical insulation with a support frame can be ensured.

  As shown in FIG. 1, the tab electrode 106 is disposed at both ends of the photoelectric conversion device 100 so as to electrically connect the photoelectric conversion cell groups divided in parallel by the slits S5 in parallel. The tab electrode 106 is formed in a direction parallel to the slit S4. The tab electrode 106 can be made of a material containing a conductive metal such as copper (Cu), silver (Ag), or aluminum (Al). For example, a structure in which the surface of a core wire made of copper (Cu) is coated (plated) with solder is suitable.

  As shown in FIGS. 1, 2, and 4, the tab electrode 106 is electrically connected to the back electrode layer 20 of a plurality of photoelectric conversion cells connected in series at both ends of the photoelectric conversion device 100. It is formed. The tab electrode 106 is provided for collecting the electric power generated in the photoelectric conversion apparatus 100 to the extraction electrode 108.

  The tab electrode 106 is formed on a photoelectric conversion cell in a region (ineffective region) that does not contribute to power generation. The tab electrode 106 is bonded to the transparent electrode layer 12 by melting the conductive metal using an ultrasonic soldering iron and reaching the transparent electrode layer 12.

  The extraction electrode 108 is provided for electrically connecting the tab electrode 106 to the terminal box 120 as shown in FIGS. 1 and 4. The extraction electrode 108 is formed from the tab electrode 106 to the terminal box 120 in the direction along the slits S2 and S5. The insulating member 104 is formed under a region where the extraction electrode 108 is formed so that a plurality of photoelectric conversion cells connected in series do not contact the extraction electrode 108. The extraction electrode 108 is disposed on the insulating member 104, and a tab electrode 107 described later is disposed below the insulating member 104. The insulating member 104 is preferably a tape-like, film-like or sheet-like member made of an insulating material, for example.

  As shown in FIGS. 1 and 2, the tab electrode 107 is disposed between the tab electrodes 106 at both ends so that a plurality of bypass diodes 114 are connected in parallel. The tab electrode 107 is installed for every predetermined number of the plurality of photoelectric conversion cells connected in series between the tab electrodes 106 at both ends. As with the tab electrode 106, the tab electrode 107 is disposed so as to electrically connect the photoelectric conversion cell groups arranged in parallel. It is formed in a direction parallel to the slit S4. The tab electrode 107 can be made of a material containing a conductive metal such as copper (Cu), silver (Ag), or aluminum (Al). For example, a structure in which the surface of a core wire made of copper (Cu) is coated (plated) with solder is suitable.

  The tab electrode 107 is formed on a photoelectric conversion cell in a region (effective region) that contributes to power generation. As shown in FIGS. 1, 3, and 4, the tab electrode 107 is electrically connected to the back electrode layer 20 of the plurality of photoelectric conversion cells connected in series between the tab electrodes 106 at both ends. Formed. The tab electrode 107 is provided to collect power in the bypass diode 114 when a hot spot phenomenon occurs.

  The tab electrode 107 is preferably a conductive tape in which a conductive adhesive layer 107a and a conductive foil 107b are laminated. For example, an acrylic adhesive resin can be applied to the conductive adhesive layer 107a. As the conductive foil 107b, for example, a tin-plated copper foil or the like can be used. However, it is not limited to these. The tab electrode 107 may be a conductive tape in which a conductive adhesive layer 107a containing conductive particles and a conductive foil 107b are laminated. In this case, after the tab electrode 107 is attached, the resin in the conductive adhesive layer 107a is cured by performing a heat treatment. However, it is not limited to these.

  The tab electrode 106 and the extraction electrode 108 may also be a conductive tape in which the conductive adhesive layers 106a and 108a and the conductive foils 106b and 108b are laminated.

  When a method of connecting the tab electrode 107 made of solder material to the back electrode layer 20 with ultrasonic soldering or the like is used, the characteristics of the connected photoelectric conversion cell may be deteriorated. By using this, a bypass circuit can be provided without deteriorating the characteristics of the photoelectric conversion cell.

  The insulating member 110 is formed under a region where the bypass electrode 112 is formed so that the photoelectric conversion cell does not contact the bypass electrode 112. The insulating member 110 is preferably a tape-like, film-like or sheet-like member made of an insulating material, for example. The insulating member 110 extends on the back electrode layer 20 of the photoelectric conversion device 100 along the serial connection direction of the photoelectric conversion cells, that is, in the direction along the slits S2 and S5.

  The bypass diode 114 is disposed on the insulating member 110 between the tab electrodes 106 and 107 or between the adjacent tab electrodes 107. The bypass diode 114 is provided to prevent damage to the photoelectric conversion cell when a hot spot occurs in the photoelectric conversion device 100. As the bypass diode 114, for example, a thin chip diode having cathode and anode electrodes on the front and back surfaces can be applied. The bypass diode 114 is connected to the photoelectric conversion cell by the bypass electrode 112 so that the voltage is applied in a reverse bias state in a state where the photoelectric conversion cell is normally generating power. That is, the anode and cathode of the bypass diode 114 are connected to the adjacent tab electrodes 106 and 107 by the bypass electrode 112, respectively. The connection between the bypass electrode 112 and the bypass diode 114 may be performed by general soldering or mechanical crimping by sealing using the back sheet 116 and the filler 118.

  The bypass electrode 112 may also be a conductive tape in which a conductive adhesive layer 112a and a conductive foil 112b are laminated.

  In the present embodiment, the bypass circuit including the bypass electrode 112 and the bypass diode 114 is formed on the same straight line. However, the positions of the bypass electrodes 112 and the bypass diode 114 are shifted from the same straight line. Also good.

  Further, the surface of the photoelectric conversion device 100 is covered with a back sheet 116 and sealed with a filler 118. The filler 118 and the back sheet 116 can be made of a resin material such as EVA or polyimide. Further, the back sheet 116 may be a glass plate or the like. Sealing can be performed by covering the back electrode layer 20 coated with the filler 118 with the back sheet 116 and applying pressure to the back sheet 116 toward the back electrode layer 20 while heating to a temperature of about 150 ° C. . This can prevent moisture from entering the power generation layer of the photoelectric conversion device 100.

  As described above, in the photoelectric conversion device 100 according to the present embodiment, the bypass circuit including the tab electrode 107, the bypass electrode 112, and the bypass diode 114 is arranged in the region where the photoelectric conversion unit is formed. By not arranging the bypass diode 114 outside the region where the photoelectric conversion unit is formed, the power generation efficiency per installation area as the photoelectric conversion device 100 can be improved.

  Further, when the wiring portion including the insulating member 104 and the extraction electrode 108 and the bypass circuit including the bypass electrode 112 and the bypass diode 114 are arranged close to one side of the photoelectric conversion device 100, the region where these are not provided A step is generated between them, and the inclination of the back sheet 116 with respect to the substrate 10 increases. Such inclination makes the stress applied to the photoelectric conversion device 100 non-uniform and may cause damage or deterioration. Therefore, the bypass circuit is preferably provided in a region (a lower region in FIG. 1) on the opposite side of the center line X of the photoelectric conversion device 100 with respect to a region (an upper region in FIG. 1) where the wiring portion is provided. is there. With such an arrangement, the back sheet 116 can be provided in a more balanced manner with respect to the substrate 10 by the step due to the wiring portion and the step due to the bypass circuit.

  In addition, as shown in FIG. 1, when the tab electrode 107 is extended to a position opposite to the place where each bypass diode 114 is installed, a hot spot phenomenon occurs and a predetermined bypass diode 114 is used. However, current extraction to the bypass diode 114 can be performed with low resistance.

  10 Substrate, 12 Transparent electrode layer, 14 a-Si unit, 16 Intermediate layer, 18 μc-Si unit, 20 Back electrode layer, 100 Photoelectric conversion device, 102 Photoelectric conversion unit, 104 Insulating member, 106 Tab electrode, 106a Conductivity Adhesive layer, 106b Conductive foil, 107 Tab electrode, 107a Conductive adhesive layer, 107b Conductive foil, 108 Extraction electrode, 108a Conductive adhesive layer, 108b Conductive foil, 110 Insulating member, 112 Bypass electrode, 112a Conductive adhesive layer, 112b Conductive foil, 114 bypass diode, 116 backsheet, 118 filler, 120 terminal box.

Claims (4)

A photoelectric conversion device having a photoelectric conversion unit formed by connecting a plurality of photoelectric conversion cells including a thin film semiconductor layer in series on a substrate,
The photoelectric conversion device, wherein the photoelectric conversion cell is connected to a plurality of bypass diodes through an electrode made of a conductive tape in a region where the photoelectric conversion unit is formed. The photoelectric conversion device according to claim 1,
The bypass diode is installed for every predetermined number of the photoelectric conversion cells, and is connected in parallel in the photoelectric conversion unit. The photoelectric conversion device according to claim 1, wherein
The said electroconductive tape is extended and provided along the direction which cross | intersects the serial connection direction of the said photoelectric conversion cell, and is connected with the back surface electrode layer of the said photoelectric conversion cell, The photoelectric conversion apparatus characterized by the above-mentioned. It is a photoelectric conversion device given in any 1 paragraph of Claims 1-3,
The bypass circuit including the bypass diode is arranged in a region on the opposite side of the center line of the photoelectric conversion device with respect to a region provided with a tab electrode connected to a terminal box for taking out power to the outside. A photoelectric conversion device.

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